Television camera tube with mounting assembly for grid adjacent photoconductor

ABSTRACT

A television camera tube having an elongate envelope comprising two cylindrical parts. The cylindrical part which is connected to the face plate has a larger diameter than the other cylindrical part and comprises a gauze electrode secured to a supporting ring. This supporting ring is clamped between the face plate and the neck between the two cylindrical parts by means of resilient pressure means. A circular rounding of the neck on the side of the cylindrical part with the smallest diameter is to be preferred, said rounding being covered with a conductive layer. A few dimensions are given related to the diameter of the cylindrical part of the smallest diameter. The ratio between the voltages at the gauze electrode and the conductive layer preferably is between 1.65 and 2.35.

United States Patent [191 Van Roosmalen et al.

[451 Apr. 2, 1974 [73] Assignee: U.S. Philips Corporation, New

York, N.Y.

[22] Filed: Aug. 30, 1971 [21] Appl. No.: 176,012

[30] Foreign Application Priority Data Sept. 4, 1970 Netherlands 7013097 [52] U.S. Cl 313/65 A [51] Int. Cl H01] 31/38, HOlj 29/02 [58] Field of Search.. 313/65 A, 65 T, 65 R, 65 LF, 313/66, 67, 94, 283, 102

[56] References Cited UNITED STATES PATENTS 3,375,391 3/1968 Day 313/102 X 3,437,860 4/1969 Ney 313/65 R 2,036,532 4/1936 Knoll et al. 313/66 X 2,908,835 10/1959 Weimer 313/65 A 2,917,574 12/1959 313/65 R X 3,300,669 l/l967 Jordan 313/65 A 3,249,785 5/1966 Floyd et al. 313/65 T FOREIGN PATENTS OR APPLICATIONS 1,097,587 l/1968 Great Britain 313/65 A Primary Examiner-Robert Segal Attorney, Agent, or Firm-Carl P. Steinhauser; Frank R. Trifari [5 7 ABSTRACT A television camera tube having an elongate envelope comprising two cylindrical parts. The cylindrical part which is connected to the face plate has a larger diameter than the other cylindrical part and comprises a gauze electrode secured to a supporting ring. This supporting ring is clamped between the face plate and the neck between the two cylindrical parts by means of resilient pressure means. A circular rounding of the neck on the side of the cylindrical part with the smallest diameter is to be preferred, said rounding being covered with a conductive layer. A few dimensions are given related to the diameter of the cylindrical part of the smallest diameter. The ratio between the voltages at the gauze electrode and the conductive layer preferably is between 1.65 and 2.35.

4 Claims, 2 Drawing Figures PATENTEDAPR 2 1914 3. 8 O 1.848

sum 1 or 2 AG ENT TELEVISION CAMERA TUBE WITH MOUNTING ASSEMBLY FOR GRID ADJACENT PHOTOCONDUCTOR The invention relates to a television camera tube comprising in an elongate mainly rotationally symmetrical evacuated envelope an electron gun, a photoconductive layer provided on a face plate forming part of the envelope, and a gauze electrode secured to a supporting ring parallel to and in the immediate proximity of the photoconductive layer, said envelope comprising a first substantially cylindrical part, a second substantially cylindrical part connected to the face plate and a neck which connects the two cylindrical parts together.

The electron gun in such a television camera tube produces an electron beam which generally is focused on the photoconductive layer by a focusing lens and which scans the photoconductive layer in a pattern of parallel lines under the influence of deflection means. It is of importance that the axis of the electron beam should always be perpendicular to the photoconductive layer, independent of the deflection of the electron beam. For this purpose, the said gauze electrode is present at a few mms in front of the photoconductive layer. As a result of electric voltages on the electrodes of the tube, an electric field is formed on the side of the gauze electrode remote from the photoconductive layer, which field exerts a lens effect on the electron beam as a result of which the axis thereof is always substantially perpendicular to the gauze electrode. This lens effect will hereinafter be termed gauze lens. The electrons furthermore experience an inhibiting field be tween the gauze electrode and the photoconductive layer. In combination with the adjustment of the focusing by means of the focusing lens, this inhibiting field ensures that the electron beam impinges upon the photoconductive layer with a spot which is as small as possible. It is obvious that it is of importance for the said inhibiting field that the distance between the gauze electrode and the photoconductive layer be accurately fixed. Furthermore the accuracy of the configuration of the gauze lens should also fulfil very high requirements. Television camera tubes of the described construction generally are vidicons.

A television camera tube of the above-described type is described in the US. Pat. specification No. 2,770,746. The face plate in this tube does not form one assembly with the second cylindrical part but is secured thereto by glue or a solder glass. The gauze electrode in this tube is secured to the face plate. The tube furthermore comprises a conductive layer which internally covers a part of the first cylindrical part, the neck, and a part of the second cylindrical part. The connection of the gauze electrode to the face plate, and that with the required accuracy, does not favour the simplicity of the manufacturing process of the said tube.

One object of the invention is to provide a television camera tube of the type mentioned in the first paragraph of such a construction that both a very simple assembly and a very accurately determined configuration of the gauze ends and a very accurately determined distance between the gauze electrode and the photoconductive layer are obtained. Another object of the invention is to make optimum use of the diameter of the second cylindrical part, so that a part of the face plate which is as large as possible can be used for projecting on it an optical image. A further object of the invention is to provide a configuration for the gauze lens which satisfies very high electron optical requirements.

According to the invention, a television camera tube having in an elongate mainly rotationally symmetrical evacuated envelope an electron gun, a photoconductive layer provided on a face plate forming part of the envelope and a gauze electrode secured to a supporting ring and parallel to and in the immediate proximity of the photoconductive layer, said envelope comprising a first, substantially cylindrical part, a second substantially cylindrical part connected to the face plate and having a larger diameter than the first cylindrical part, and a neck which connects the two cylindrical parts together, is constructed so that the supporting ring is clamped between the face plate and the neck by means of resilient pressure means.

As a result of this construction, the number of manipulations to which the face plate comprising the photoconductive layer and the gauze electrode has to be subjected is minimized. This is of great importance since the photoconductive layer and the gauze electrode are very sensitive to dust. As a result of the construction according to the invention it is possible to vapourdeposit the photoconductive layer on the face plate under optimum conditions, and to assemble the gauze electrode and the face plate with the photoconductive layer only in an advanced stage of the manufacturing process of the television camera tube.

A television camera tube according to the invention is preferably constructed so that an insulation ring is present between the inside of the neck and the supporting ring, and that the resilient pressure means are present between the target and the supporting ring, said means clamping the insulation ring between the neck and the supporting ring.

In this manner the required small tolerances which hold good for the gauze lens and the distance between the gauze electrode and the photoconductive layer are obtained in a very simple manner. The correct diameter of the two cylindrical pans and the correct shape of the neck can actually be obtained in a simple manner by giving a glass component manufactured with wide tolerances the required dimensions on an accurately manufactured jig by means of negative pressure and heating. The length of the second cylindrical part is then determined accurately by grinding. The distance between the neck and the gauze electrode which is decisive of the gauze lens, as well as the distance between the gauze electrode and the photoconductive layer are then further determined only by the dimensions of the supporting ring and the insulation ring, which can of course be manufactured very accurately in a simple manner.

A television camera tube according to the invention comprising a focusing lens and a conductive layer on a part of the inside of the envelope is further manufactured preferably so that the neck, in a cross-section which comprises the axis of the envelope, comprises a part which has the shape of two quarter circles present each on one side of the axis and adjoining the first cylindrical part, which part of the neck is coated on the inside with the conductive layer, which layer also covers a part of the first cylindrical part and is connected to the last electrode of the focusing lens, that the radius of the said quarter circles is between 0.14 and 0.28 times the inside diameter of the first cylindrical part,

that the distance from the tangent line at the said quarter circles parallel to the gauze electrode to the plane bounding the supporting ring on the side of the electron gun is between 0.05 and 0.09 times the inside diameter of the first cylindrical part, that the distance from the plane which bounds the supporting ring on the side of the electron gun to the gauzeelectrode is between and 0.2 times the inside diameter of the first cylindrical part, and that the inside diameter of the part of the supporting ring present on the side of the electron gun is between 1.06 and 1.36 times the inside diameter of the first cylindrical part.

Experiments have demonstrated that a tube of the above dimensions has a gauze lens which satisfies very high requirements both as regards the perpendicular position of the axis of the beam on the gauze electrode and as regards the distortion which might occur by a gauze lens which does not have the correct configuration.

A television camera tube according to the invention comprising deflection coils is preferably constructed so that the distance between the deflection center of the deflection coils and the gauze electrode is between 1.43 and 2.13 times the inside diameter of the first cylindrical part.

The distance between the deflection center and the gauze electrode is of importance not only for the gauze lens but in the said experiments it has also been found that it is possible in this manner to cause the small distortion which the gauze lens still has and which is a socalled barrel distortion, to be removed considerably by a small pincushion distortion of the deflection coils.

A device having a television camera tube according to the invention is preferably constructed so that the voltage at the gauze electrode is between 1.65 and 2.35 times as high as the voltage at the conductive layer.

Of course, the correct effect of the gauze lens also depends upon the voltages at the electrodes between which the said ratio should preferably exist.

The invention will now be described with reference to the accompanying drawing, in which:

FIG. 1 shows the television camera tube according to the invention, and

FIG. 2 shows the front part of the said tube on an enlarged scale.

The camera tube shown in FIG. 1 is of the PLUMBI- CON type and comprises a glass envelope 1 having on one side a face plate 2, on which a layer 3 is provided which consists of a photoconductive layer and a conductive transparent signal plate between the photoconductive layer and the face plate 2. The photoconductive layer mainly consists of specially activated lead monoxide and the signal plate of conductive tin dioxide. The connection pins 4 of the tube are present on the other side of the envelope 1. The camera tube comprises an electron gun 6 and a focusing lens 7 centered along an axis 5. The tube furthermore comprises a gauze electrode 8. A set of deflection coil 9, which are shown diagrammatically and deflect the electron beam produced by the electron gun 6 in two mutually perpendicular directions, are arranged around the envelope l. The deflection center of the coils 9 is denoted by 22. The outside diameter of the deflection coils 9 is not larger than the outside diameter of the front part 13 of the tube. A conductive layer is present on a part of the inner wall of the envelope 1 and is connected to the last electrode 12 of the focusing lens 7 by means of the connection 11.

FIG. 2 shows the front part of the camera tube, which is denoted by 13 in FIG. 1, on an enlarged scale. The neck of the tube comprises a rounding which is formed by the quarter circle of radius R. This rounding is also covered with the conductive layer 10. The gauze electrode 8 is mounted in a supportingring which consists of the parts 19 and 20. The supporting ring is centered relative to the axis 5 by means of a centering ring 16. Two platinum pins 17 and 18 are sealed in the envelope 1 and constitute the connection of the gauze electrode 8. The supporting ring (19, 20) is held in its space by means of a pressure ring 14, a spring ring 15 and an insulation ring 21. In addition to the radius R, a few other distances are shown in the Figure. A is the thickness of the ring 20, B is the thickness of the ring 21, C is the inside diameter of the ring 20, M is the distance from the deflection center 22 to the gauze electrode 8, and D is the inside diameter of the envelope 1. For optimum effect of the gauze lense, said sizes can be expressed as follows in D.

R 0.21 10.07 x D,

A 0.1 10.1 x D,

B 0.07 i 0.02 x D, c= 1.21 i 0.15 x D,

M=(l.78 i 0.35 X D.

For an optimum effect of the gauze lens it should furthermore hold that V (2.0 i 0.35) V where V is the voltage at the conductive layer 10 and V is the voltage at the gauze electrode 8. For the camera tube shown it holds that:

D=l4mm, C=l8 mm,

R=3mm, M=25mm,

A=lmm, V =500 V,

B= 1 mm, V 1,000 V.

In assembling the tube, the face plate 2 with the layer 3 is adhered to the rest of the envelope 1 by means of glue or enamel. This is carried out only in an advanced stage of the manufacture when the electrode system has been scaled and cleaned.

What is claimed is:

l. A television camera tube having in an elongate substantially rotationally symmetrical evacuated envelope an electron gun, a photoconductive layer provided on a face plate forming part of the envelope, and a gauze electrode secured between two rings forming a supporting ring parallel to and in the immediate proximity of the photoconductive layer, said envelope comprising a first substantially cylindrical part, a second substantially cylindrical part connected to the face plate and having a larger diameter than the first cylindrical part, an insulation ring adjacent said transition I portion, and a transition portion which connects the two cylindrical parts together, said supporting ring having an outside diameter which is larger than the inside diameter of said first cylindrical part, a pressure ring adjacent said face plate, and resilient pressure means clamping said supporting ring between said pressure ring and said insulation ring.

2. A television camera tube as claimed in claim 1 comprising a focusing lens having a plurality of electrodes one of which is a last electrode and a conductive layer on a part of the inside of the envelope, and wherein the transition portion, in a cross-section which includes the axis of the envelope, comprises a part which has the shape of two quarter circles present each on one side of the axis and adjoining the first cylindrical part, said part of the transition portion being coated on the inside with the conductive layer, said layer also covering a part of the first cylindrical part and being connected to the last electrode of the focusing lens, the radius of the said quarter circles being between 0.14 and 0.28 times the inside diameter of the first cylindrical part, the distance from the tangent line at the said quarter circles parallel to the gauze electrode to the plane bounding the supporting ring on the side of the electron gun being between 0.05 and 0.09 times the inside diameter of the first cylindrical part, the distance from the plane which bounds the supporting ring on the side of the electron gun to the gauze electrode being between 0 and 0.2 times the inside diameter of the first cylindrical part, and the inside diameter of the part of the supporting ring, present on the side of the electron gun being between 1.06 and 1.36 times the inside diameter of the first cylindrical part.

3. A television camera tube as claimed in claim 2 comprising deflection coils, the distance between the deflection center of the deflection coils and the gauze electrode being between 1.43 and 2.13 times the inside diameter of the first cylindrical part.

4. A device comprising a television camera tube as claimed in claim 2, and means to apply voltages to the gauze electrode and conductive layer, the voltage applied to the gauze electrode being between 1.65 and 2.35 times as high as the voltage at the conductive layer. 

1. A television camera tube having in an elongate substantially rotationally symmetrical evacuated envelope an electron gun, a photoconductive layer provided on a face plate forming part of the envelope, and a gauze electrode secured between two rings forming a supporting ring parallel to and in the immediate proximity of the photoconductive layer, said envelope comprising a first substantially cylindrical part, a second substantially cylindrical part connected to the face plate and having a larger diameter than the first cylindrical part, an insulation ring adjacent said transition portion, and a transition portion which connects the two cylindrical parts together, said supporting ring having an outside diameter which is larger than the inside diameter of said first cylindrical part, a pressure ring adjacent said face plate, and resilient pressure means clamping said supporting ring between said pressure ring and said insulation ring.
 2. A television camera tube as claimed in claim 1 comprising a focusing lens having a plurality of electrodes one of which is a last electrode and a conductive layer on a part of the inside of the envelope, and wherein the transition portion, in a cross-section which includes the axis of the envelope, comprises a part which has the shape of two quarter circles present each on one side of the axis and adjoining the first cylindrical part, said part of the transition portion being coated on the inside with the conductive layer, said layer also covering a part of the first cylindrical part and being connected to the last electrode of the focusing lens, the radius of the said quarter circles being between 0.14 and 0.28 times the inside diameter of the first cylindrical part, the distance from the tangent line at the said quarter circles parallel to the gauze electrode to the plane bounding the supporting ring on the side of the electron gun being between 0.05 and 0.09 times the inside diameter of the first cylindrical part, the distance from the plane which bounds the supporting ring on the side of the electron gun to the gauze electrode being between 0 and 0.2 times the inside diameter of the first cylindrical part, and the inside diameter of the part of the supporting ring, present on the side of the electron gun being between 1.06 and 1.36 times the inside diameter of the first cylindrical part.
 3. A television camera tube as claimed in claim 2 comprising deflection coils, the distance between the deflection center of the deflection coils and the gauze electrode being between 1.43 and 2.13 times the inside diameter of the first cylindrical part.
 4. A device comprising a television camera tube as claimed in claim 2, and means to apply voltages to the gauze electrode and conductive layer, the voltage applied to the gauze electrode being between 1.65 and 2.35 times as high as the voltage at the conductive layer. 